This invention relates generally to protecting reticles from particle contamination, for example during transportation.
Reticles are patterned devices that can be exposed to transfer a pattern on the reticle to a semiconductor structure. Through the use of reticles, patterns may be repeatedly transferred to semiconductor structures in an automated process. This greatly reduces the cost of forming integrated circuits.
Reticles are transported in a shipping container. Physical protection is provided by a shipping box. The reticle carrier that actually carries the reticle may be contained within an antistatic bag.
Conventional packaging is sufficient for optical reticles whose minimum printable particle size is roughly 30 microns. In such case, any particle smaller than 30microns would not adversely affect the operation of the reticle.
However, with certain advanced lithography reticles, such as extreme ultraviolet (EUV) reticles, the technology is capable of resolving particles on the reticle that are much smaller than 30 microns. In these technologies, it is desirable to maintain the reticle free of particles greater than 30 to 50 nanometers in size.
Current mechanical protection methods may be inadequate to prevent small particles from landing on the reticles. If particles landing on the reticle are large enough to adversely affect the transfer of the pattern from the reticle to the semiconductor structure, the reticle must be cleaned. Effective techniques for removing such small particles are largely unproven.
Thus, there is a need for better ways to remove particles from reticles.